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Commit 2467658e authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Introduce i915_gem_active_wait_unlocked() 



It is useful to be able to wait on pending rendering without grabbing
the struct_mutex. We can do this by using the i915_gem_active_get_rcu()
primitive to acquire a reference to the pending request without
requiring struct_mutex, just the RCU read lock, and then call
i915_wait_request().

v2: Rebase onto new i915_gem_active_get_unlocked() semantics that take
the RCU read lock on behalf of the caller.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-1-git-send-email-chris@chris-wilson.co.uk
parent 94558e26

drivers/gpu/drm/i915/i915_gem_request.h

+40 −0
Original line number Diff line number Diff line
@@ -568,6 +568,46 @@ i915_gem_active_wait(const struct i915_gem_active *active, struct mutex *mutex) 
	return i915_wait_request(request, true, NULL, NULL);

}



/**

 * i915_gem_active_wait_unlocked - waits until the request is completed

 * @active - the active request on which to wait

 * @interruptible - whether the wait can be woken by a userspace signal

 * @timeout - how long to wait at most

 * @rps - userspace client to charge for a waitboost

 *

 * i915_gem_active_wait_unlocked() waits until the request is completed before

 * returning, without requiring any locks to be held. Note that it does not

 * retire any requests before returning.

 *

 * This function relies on RCU in order to acquire the reference to the active

 * request without holding any locks. See __i915_gem_active_get_rcu() for the

 * glory details on how that is managed. Once the reference is acquired, we

 * can then wait upon the request, and afterwards release our reference,

 * free of any locking.

 *

 * This function wraps i915_wait_request(), see it for the full details on

 * the arguments.

 *

 * Returns 0 if successful, or a negative error code.

 */

static inline int

i915_gem_active_wait_unlocked(const struct i915_gem_active *active,

			      bool interruptible,

			      s64 *timeout,

			      struct intel_rps_client *rps)

{

	struct drm_i915_gem_request *request;

	int ret = 0;



	request = i915_gem_active_get_unlocked(active);

	if (request) {

		ret = i915_wait_request(request, interruptible, timeout, rps);

		i915_gem_request_put(request);

	}



	return ret;

}



/**

 * i915_gem_active_retire - waits until the request is retired

 * @active - the active request on which to wait